Module 2.2.2-2.2.3 Kinetics and dynamics

Kinetics describes motion (speed, acceleration, rotation, vibration); dynamics links motion to forces, work, energy and momentum.

Knowledge levels

Item	A	B1	B2 / B2L	B3
2.2.2 Kinetics: linear, rotational and periodic motion, vibration, resonance, velocity ratio, mechanical advantage, efficiency	1	2	2	1
2.2.3(a) Mass, force, inertia, work, power, energy, heat, efficiency	1	2	2	1
2.2.3(b) Momentum, impulse, gyroscopic principles, friction	1	2	2	1

Linear motion

• Speed = distance / time (scalar). Velocity = speed in a given direction (vector).
• Acceleration a = change in velocity / time (m/s²).

Equations of uniformly accelerated motion (u = initial velocity, v = final velocity, s = distance, t = time):

Equation	Use when you do not know
v = u + at	s
s = ut + ½at²	v
v² = u² + 2as	t
s = ½(u + v)t	a

Worked example - braking distance

An aircraft lands at 60 m/s and decelerates uniformly at 3 m/s². How far does it roll to a stop?

• v² = u² + 2as → 0 = 60² − 2 × 3 × s
• s = 3 600 / 6 = 600 m

Free fall

g ≈ 9.81 m/s². A tool dropped from 20 m: v = √(2gh) = √(2 × 9.81 × 20) ≈ 19.8 m/s at impact.